1. Technical Field of the Invention
This invention relates to the manufacture of rigid polyurethane foam having fire retardancy properties. More particularly, this invention relates to a particular class of propoxylated Mannich Condensates having melamine dissolved therein and to the manufacture of rigid polyurethane foam therewith. The invention is based upon the discovery that melamine is sparingly soluble in a particular class of propoxylated Mannich Condensates and can be dissolved therein to provide modified polyols that can then be used to manufacture rigid polyurethane foams having improved fire retardancy properties.
2. Prior Art
Johnson U.S. Pat. No. 4,369,258 is directed to polyurethane foams prepared by reacting a polyisocyanate with a mixture of a melamine polyol with a polyol derived from a polyester or a polyether polyol.
Yukuta et al. U.S. Pat. No. 4,221,875 is directed to rigid polyurethane foams having flame resistance which are prepared from a mixture comprising a polyhydroxy compound such as an ethylene oxide adduct of a material containing a plurality of hydroxyl groups such as sucrose or sorbitol, an organic polyisocyanate, a blowing agent and powdered melamine. From 20 to 60 parts by weight of powdered melamine per 100 parts of polyhydroxy compound are recommended.
Pcolinsky, Jr. U.S. Pat. No. 4,317,889 and the numerous U.S. patents cited therein disclose the use of melamine derivatives such as hydroxymethyl melamines, melamine phosphate, hexaalkoxymethylmelamine, etc. as components for use in the manufacture of flexible polyurethane foams.
Jacobs et al. U.S. Pat. No. 4,312,988 is directed to the synthesis of hydroxy-terminated melamine derivaties by reacting melamine with isopropanolamine rather than ethanolamine in order to prevent the isomelamine-forming side reactions that can occur when ethanolamine is used. There is no mention in the reference of the use of the hydroxy-terminated melamine derivatives to form polyurethanes.
It is to be noted that none of the above-mentioned references indicate that melamine is soluble in polyols used in the manufacture of polyurethanes. The teachings of the references is to the contrary.
Edwards et al. U.S. Pat. No. 3,297,597 is directed to Mannich condensates of a phenolic compound, formaldehyde, and an alkanolamine which are then alkoxylated, preferably with propylene oxide, to provide polyols useful in the manufacture of rigid polyurethane foams.
Edwards et al. U.S. Pat. No. 4,137,265 is similarly directed to Mannich condensates prepared by reacting nonylphenol with formaldehyde and diethanolamine which are then propoxylated and used in the manufacture of rigid polyurethane foam.